Researchers Report On Caloric, Bacterial Content Of Bully Sticks

Published: 2013.01.28 11:32 AM

Tufts and University of Guelph researchers reported today that many veterinarians and pet owners could not identify the source of bully sticks and did not realize that the popular dog treats quickly add calories to an animal’s diet.

The study, published in the January issue of the Canadian Veterinary Journal, also noted that some of the bully sticks tested were contaminated by bacteria.

Bully, or pizzle, sticks are made from the uncooked, dried penis of a bull or steer.

Tasty bully sticks can add calories and carry bacteria.

The researchers, representing the Cummings School of Veterinary Medicine at Tufts University and the University of Guelph, examined 26 bully sticks purchased from retailers in the United States and Canada and made by different manufacturers. Random testing of the bully sticks found that they contained from nine to 22 calories per inch, or 88 calories in the average 6-inch stick.

Eighty-eight calories is equal to 9 percent of the daily calorie requirements for a 50-pound dog and 30 percent for a 10-pound dog, the researchers stated.

“While calorie information isn’t currently required on pet treats or most pet foods, these findings reinforce that veterinarians and pet owners need to be aware of pet treats like these bully sticks as a source of calories in a dog’s diet,” said Lisa M. Freeman, DVM, Ph.D., Dipl. ACVN, a professor of nutrition at Tufts.

“With obesity in pets on the rise, it is important for pet owners to factor in not only their dog’s food, but also treats and table food,” Dr. Freeman added.

She co-authored the paper with J. Scott Weese, DVM, DVSc, Dipl. ACVIM, a professor in the Department of Pathobiology at the University of Guelph, and Nicol Janecko, a research associate at the Canadian university.

All 26 treats were tested for bacterial contaminants. One stick contained Clostridium difficile; one had methicillin-resistant Staphylococcus aureus (MRSA), a staph bacterium resistant to certain antibiotics; and seven had Escherichia coli, including one tetracycline-resistant sample.

The researchers acknowledged the small sample size and that not all of the bacterial strains discovered are shown to infect humans.

The study included a 20-question Web-based survey designed to measure veterinarian and pet owner perceptions of dog foods and treats. More than 850 adults, mostly female dog owners, responded from 44 states and six countries.

“We were surprised at the clear misconceptions pet owners and veterinarians have with pet foods and many of the popular raw animal product-based pet treats currently on the market,” Freeman said. “For example, 71 percent of people feeding bully sticks to their pets stated they avoid byproducts in pet foods, yet bully sticks are, for all intents and purposes, an animal byproduct.”

When it came to identifying the source of bully sticks, the researchers said they were surprised. Only 62 percent of veterinarians knew that a bully stick came from a bull penis, compared to 44 percent of the general respondents.

Twenty-three percent of the respondents reported feeding bully sticks to their dogs.

Further research with a larger sample size is needed to determine whether the reported calorie content and contamination rate are representative of all bully sticks and other types of pet treats, the authors added.